The invention is in the field of disposable hypodermic syringes for injecting medication into patients. In particular, the invention is directed to a simplified, economical means of adapting existing syringes to capture the needle cannula and retrieve it into the cylinder of the syringe in a safe manner after expulsion of medicament.
Disposable hypodermic syringes are routinely used to administer medication to patients, thus presenting the requirement for proper disposal of used and contaminated needles. In an emergency situation, this requirement sometimes is overlooked by the caregiver, whether for practical reasons or otherwise. Separate procedures for disposal are limited at best, consisting of (i) breaking the needle off in a special container which is separate from the syringe, or (ii) using special equipment to assemble or disassemble the syringe, both of which require extra steps for proper disposal of the contaminated device.
Even needles which are broken off still can present a hazard of so-called "needle strikes" to trash removal personnel. The potential for needle strikes to health caregivers and associated personnel can cause a high degree of anxiety and require expensive testing procedures of suspected needle strikes. More and more health care personnel are exposed to the risk of infection with the increasing care requirements of HIV- and AIDS-infected individuals, as well as the risk of hepatitis B and other infectious diseases.
Prior attempts to address safe disposal of contaminated needles by retracting the used needle into the cylinder of the syringe have required (i) redesign of the syringe, needle, and parts therein, and/or (ii) plural step disposal procedures which are not practical in emergency situations.
For instance, the above-referenced U.S. Pat. No. 4,995,870 discloses structure which requires loosening of the hub in order to release the needle from a plug and thus allow for withdrawal of the used needle into the cylinder of the syringe. While manipulating the hub to allow for the retraction, the caregiver must either expose his/her hand to the distal end of the used and possibly contaminated needle or use an auxiliary device for covering the tip of the used needle.
The needles of above-referenced U.S. Pat. Nos. 4,026,287; 4,804,370; and 5,221,262 all are integral with the syringe cylinder rather than being removably attachable assemblies and, thus, prevent adaptability to syringes having the so-called Luer lock connection or other types of removable attachments for non-integral needle assemblies.
Some prior art devices have so-called extended needles which protrude proximally into the syringe cylinder past their points of attachment to the needle assembly such that complete expulsion of fluid from a cylinder is negated. Since fluid is not compressible, any residual fluid in the distal end of the cylinder opposes further distal movement of the piston once the proximal opening of the needle is blocked by the piston or otherwise. Under this condition, further distal movement of the piston and capturing of the extended needle for retraction is rendered non-functional or, at best, difficult.
Some prior art devices also provide for a barbed, proximal end of the extended needle be impaled in a full (as opposed to hollow) piston or the like to effect capture and retraction, thus requiring more force to effect the capture.
The needle capturers of the prior art are integral with the corresponding piston stems and, thus, do not present structure which lends it self to retrofitting to existing piston stems of particular syringes which are widely used in the industry.
Thus, it is an object of the invention to provide means for converting most non-retracting hypodermic syringes currently on the market to retractable safety syringes, with only minor, non-disruptive changes in the manufacturing process.
Further, it is an object of the invention to provide a separately attachable capturing device for retrofitting to a syringe without altering the structure of an already existing means for attaching the rubber piston to the piston stem.
Still further, it is an object of the invention to provide an add-on needle capturer which is receivable in the existing rubber piston of a syringe and at least partially retained therein by the existing means of attaching the rubber piston to the end of the stem.
Also, it is an object of the invention to modify or replace existing needles, with so-called extended needles having side ports so as to provide for complete expulsion of fluid from the cylinder and capture of the needle without difficulty, in a manner which also provides for canting of the retracted needle.
Additionally, it is an object of the invention to provide an audible indicator which, in one form, signals the actual capture of the needle and, in another form, signals that the piston has displaced sufficiently distally for capture of the needle to have taken place.
These and other objects will become more apparent from a detailed study of the remaining disclosure.